U.S. patent application number 11/107631 was filed with the patent office on 2005-08-18 for tensioner for a traction drive.
This patent application is currently assigned to INA-SCHAEFFLER KG. Invention is credited to Konanz, Holger.
Application Number | 20050181902 11/107631 |
Document ID | / |
Family ID | 32049341 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050181902 |
Kind Code |
A1 |
Konanz, Holger |
August 18, 2005 |
Tensioner for a traction drive
Abstract
A tensioner for a traction drive to maintain a belt under
tension includes a base part and a pivot arm connected to the base
part for swinging about a rotation axis and having a free end for
rotatable arrangement of a roller which is supported on the power
transmitting member. A torsion spring acts on the pivot arm for
urging the roller against the belt and applies an axial force on a
damping unit for damping an adjusting movement of the pivot arm.
The damping unit includes a slitted friction bushing constructed to
have a wedge ring with conical inner and outer surfaces for
formfitting engagement in a circular ring shaped recess of the base
part or the pivot arm. The recess has contact surfaces to
complement the inner and outer surfaces of the friction bushing for
formation of two conical contact zones.
Inventors: |
Konanz, Holger; (Erlangen,
DE) |
Correspondence
Address: |
HENRY M FEIEREISEN, LLC
350 FIFTH AVENUE
SUITE 4714
NEW YORK
NY
10118
US
|
Assignee: |
INA-SCHAEFFLER KG
Herzogenaurach
DE
|
Family ID: |
32049341 |
Appl. No.: |
11/107631 |
Filed: |
April 15, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11107631 |
Apr 15, 2005 |
|
|
|
PCT/EP03/09858 |
Sep 5, 2003 |
|
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Current U.S.
Class: |
474/135 ;
474/133 |
Current CPC
Class: |
F16H 2007/081 20130101;
F16H 7/1218 20130101 |
Class at
Publication: |
474/135 ;
474/133 |
International
Class: |
F16H 007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2002 |
DE |
102 48 352.3 |
Claims
What is claimed as new and desired to be protected by Letters
Patent is set forth in the appended claims and includes equivalents
of the elements recited therein:
1. A tensioner for a traction drive to maintain a power
transmitting member, e.g. a belt, under tension, comprising: a base
part defining an axis; a pivot arm connected to the base part for
swinging about a rotation axis and having a free end for rotatable
arrangement of a roller which is supported on the power
transmitting member; a spring member acting on the pivot arm for
urging the roller against the power transmitting member; and a
damping unit acted upon by an axial force of the torsion spring for
damping an adjusting movement of the pivot arm, said damping unit
including a slitted friction bushing disposed in concentric
surrounding relationship to the rotation axis and constructed to
form a wedge ring having conical inner and outer surfaces for
formfitting engagement in a circular ring shaped recess formed in a
member selected from the group consisting of the base part and the
pivot arm, wherein the recess has contact surfaces to complement
the inner and outer surfaces of the friction bushing for formation
of two conical contact zones.
2. The tensioner of claim 1, wherein the spring member is a torsion
spring.
3. The tensioner of claim 1, wherein the inner surface and the
outer surface of the friction bushing have a same conicity.
4. The tensioner of claim 1, and further comprising a thrust washer
connected to the base part, wherein the pivot arm has a hub
rotatably supported on a pin of the base part, said friction
bushing being disposed axially between the thrust washer and the
hub.
5. The tensioner of claim 1, wherein the pivot arm has a hub
rotatably supported on a pin of the base part, said friction
bushing being disposed axially between a flange of the base part
and the hub.
6. The tensioner of claim 1, wherein the base part has a bush, and
further comprising a thrust washer connected to the base part, and
a bearing pin in fixed rotative connection with the pivot arm and
rotatably received in the bush of the base part, said friction
bushing disposed axially between the base part and the thrust
washer.
7. The tensioner of claim 1, and further comprising a thrust washer
connected in fixed rotative engagement with one member of the
group, with the recess being formed in the other member of the
group, said friction bushing being connected to the thrust
washer.
8. The tensioner of claim 7, wherein the thrust washer is connected
in fixed rotative engagement to the base part, and the recess is
formed in the swingable pivot arm for engagement by the friction
bushing.
9. The tensioner of claim 7, wherein the thrust washer is connected
in fixed rotative engagement to the pivot arm, and the recess is
formed in the base part for engagement by the friction bushing.
10. The tensioner of claim 3, wherein the conical inner and outer
surfaces of the friction bushing converge at a taper angle of
.ltoreq.35.degree..
11. The tensioner of claim 1, wherein the friction bushing is made
of plastic.
12. The tensioner of claim 1, wherein the friction bushing is made
of glass fiber reinforced plastic.
13. The tensioner of claim 1, wherein the friction bushing is made
of organic plastic.
14. The tensioner of claim 1, wherein the friction bushing is made
of two parts, comprised of a carrier and a friction lining applied
on the carrier and made of plastic.
15. The tensioner of claim 1, wherein at least one of the inner and
outer surfaces of the friction bushing is profiled or textured.
16. The tensioner of claim 1, wherein the contact surfaces of the
recess are profiled or textured.
17. The tensioner of claim 1, wherein the contact zones of the
damping unit are coated by a lubricant.
18. The tensioner of claim 1, wherein the contact zones are free of
lubricant.
19. The tensioner of claim 7, wherein the friction bushing is
formfittingly secured to the thrust washer.
20. The tensioner of claim 19, wherein the friction bushing is
connected non-detachably to the thrust washer.
21. The tensioner of claim 20, wherein the friction bushing is
connected to the thrust washer by gluing or ultrasonic welding.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of prior filed copending
PCT International application no. PCT/EP2003/009858, filed Sep. 5,
2003, which designated the United States and on which priority is
claimed under 35 U.S.C. .sctn.120, and which claims the priority of
German Patent Application, Serial No. 102 48 352.3, filed Oct. 17,
2002, pursuant to 35 U.S.C. 119(a)-(d).
BACKGROUND OF THE INVENTION
[0002] The present invention relates, in general, to a tensioner by
which a power transmitting member, e.g. a belt for a traction
drive, can be maintained under tension.
[0003] Nothing in the following discussion of the state of the art
is to be construed as an admission of prior art.
[0004] German patent publication no. DE 196 47 225A describes a
tensioner which includes a base part restrained against rotation
and a pivot arm supporting a roller which is urged against a power
transmitting member by a torsion spring arranged between the base
part and the pivot arm. The base part has a symmetry axis which
defines at the same time the rotation axis for the pivot arm. A
damping unit is arranged between the pivot arm and the rotation
axis and includes a thrust cone which engages a friction cone of
the pivot arm. The thrust cone is urged against the friction cone
by a compression spring which is placed between the thrust cone and
the base part. This prior art damping unit is complex as a result
of the great number of components, and is bulky so as to require a
large installation space for realizing a sufficient friction
surface between the thrust cone and the friction cone.
[0005] It would therefore be desirable and advantageous to provide
an improved tensioner to obviate prior art shortcomings and to
provide a compact damping unit with increased friction torque,
while still being reliable in operation.
SUMMARY OF THE INVENTION
[0006] According to one aspect of the present invention, a
tensioner for a traction drive to maintain a power transmitting
member, e.g. a belt, under tension, includes a base part, a pivot
arm connected to the base part for rotation about a rotation axis
and having a free end for rotatable arrangement of a roller which
is supported on the power transmitting member, a spring member
acting on the pivot arm for urging the roller against the power
transmitting member, and a damping unit acted upon by an axial
force of the torsion spring for damping an adjusting movement of
the pivot arm, wherein the damping unit includes a slitted friction
bushing disposed in concentric surrounding relationship to the
rotation axis and constructed to form a wedge ring having conical
inner and outer surfaces for formfitting engagement in a circular
ring shaped recess formed in a component selected from the group
consisting of the base part and the pivot arm, wherein the recess
has contact surfaces to complement the inner and outer surfaces of
the friction bushing for formation of two conical contact
zones.
[0007] The present invention resolves prior art problems by the
arrangement of a slitted friction bushing disposed in surrounding
relationship to the rotation axis of the tensioner and configured
as a wedge ring or double wedge ring. Suitably, the inner and outer
surfaces of the friction bushing have same conicity. The slitted
friction bushing can be suited in an optimum way to the
corresponding contact surfaces of the component, base part or pivot
arm, which interacts with the friction bushing. The friction
bushing effects a wanted rise of the friction torque. The damping
unit provides a separation of the functions friction generation and
sliding support between the base part and the pivot. This
functional separation has the added advantage that wear in the area
of the tapered or conical contact zones has no impact on the
right-angled disposition of the pivot arm in relation to the base
part. As a consequence of the disposition of the friction bushing
according to the invention in radially distanced surrounding
relationship to the rotation axis of the pivot bearing of the
tensioner, the damping unit has no impact on the support of the
pivot arm and no impact on the shape and length of the pivot
arm.
[0008] By arranging the friction bushing directly or indirectly
between the base part and the pivot arm, the spring member, e.g. a
torsion spring, is able to apply an axial force directly upon the
friction bushing and thus upon the conical inner and outer surfaces
of the friction bushing, thereby realizing a high friction force to
implement an effective damping of the adjusting movements of the
pivot arm. The damping unit according to the invention is hereby
applicable for any type of tensioners having a pivot arm.
[0009] According to another feature of the present invention, a
thrust washer may be connected to the base part, wherein the pivot
arm may have a hub which is rotatably supported on a pin of the
base part, thereby defining a pivot bearing, with the friction
bushing being disposed axially between the thrust washer and the
hub. Instead of the provision of a thrust washer, the base part may
also be configured with a flange, in which case the friction
bushing is disposed axially between the flange and the hub.
[0010] According to another feature of the present invention, a
bearing pin may be connected in fixed rotative engagement with the
pivot arm and rotatably received in a guide bush of the base part
to thereby define a pivot bearing, with the friction bushing
disposed axially between the base part and a flange of the pivot
arm or thrust washer connected to the pivot arm.
[0011] According to another feature of the present invention, a
thrust washer may be connected in fixed rotative engagement with
one component of the group consisting of base part and pivot arm,
with the recess being formed in the other component of the group,
wherein the friction bushing is connected to the thrust washer and
formfittingly engages the recess with the conical inner and outer
surfaces. Thus, the thrust washer may be connected in fixed
rotative engagement to the base part, and the recess may be formed
in the swingable pivot arm for engagement by the friction bushing,
or the thrust washer may be connected in fixed rotative engagement
to the pivot arm, and the recess may be formed in the base part for
engagement by the friction bushing.
[0012] According to another feature of the present invention, the
conical inner and outer surfaces of the friction bushing may
converge at a taper angle of .ltoreq.35.degree.. The friction
bushing forms a double wedge to effect a significant increase of
the friction force and to allow the wanted separation of the
functions friction generation and sliding friction of the
tensioner. System-based wear of the friction surfaces of the
friction bushing thus has no impact on the right-angled disposition
of the moving components of the tensioner.
[0013] According to another feature of the present invention, the
friction bushing may be made of plastic. As an alternative, the
provision of a two-part friction bushing may, of course, also be
conceivable and may involve a separate friction lining made of
plastic and applied on a bushing that forms a carrier. To optimize
wear resistance, the friction bushing may be made of glass fiber
reinforced plastic or the friction lining may be made of glass
fiber reinforced plastic. Of course, the friction bushing may be
made of any other suitable material known to the artisan that
generally follows the concepts outlined here. For example, the
friction bushing may also be made of organic plastic.
[0014] According to another feature of the present invention, the
inner surface and/or outer surface of the friction bushing may be
profiled or provided with a structure. A suitable profile involves
provision of the inner surface and/or outer surface with grooves or
indentations that radiate out, or creation of a surface with a
waffle-like texture. The profiling has hereby especially the task
to pick up wear-based abrasions from the contact zone between the
inner and outer surfaces of the friction bushing, on one hand, and
from the conical recess in the associated component, on the other
hand. The groove profile may hereby advantageously be so configured
that the abrasions move via the texture or profile, as a
consequence of the adjusting movement of the involved component,
i.e. are removed from the contact zone. Thus, the noise level is
significantly lowered.
[0015] As an alternative, or in addition to the textured inner
surface and/or outer surface of the friction bushing, it may also
be conceivable to profile the contact surface of the circular ring
shaped recess engaged by the friction bushing.
[0016] According to another feature of the present invention, the
contact zones of the damping unit may be coated or wetted by a
lubricant. The use of lubricant allows influence on the friction
torque of the damping unit and may be applied in any suitable
manner.
[0017] According to another feature of the present invention, the
friction bushing may be formfittingly secured to the respective
component of the tensioner. This ensures during assembly an
unimpeded placement of the conically extending inner and outer
surfaces in the complementary circular ring shaped recess of the
other component of the tensioner. In addition to a formfitting
connection, which for example includes partially arranged pins or
projections for engagement in respective holes of the component to
which the friction bushing is securely fixed, it is possible to
additionally secure the friction bushing by a non-detachable
connection, in particular by gluing or ultrasonic welding.
BRIEF DESCRIPTION OF THE DRAWING
[0018] Other features and advantages of the present invention will
be more readily apparent upon reading the following description of
currently preferred exemplified embodiments of the invention with
reference to the accompanying drawing, in which:
[0019] FIG. 1 is a longitudinal section of one embodiment of a
tensioner according to the present invention;
[0020] FIG. 2 is an enlarged detailed view of the area encircled in
FIG. 1 and marked "X";
[0021] FIG. 3 is a longitudinal section of another embodiment of a
tensioner according to the present invention;
[0022] FIG. 4 is an enlarged detailed view of the area encircled in
FIG. 3 and marked "Y"; and
[0023] FIG. 5 shows a sectional view of a detail showing the
tensioner of FIG. 4 with modified friction bushing.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0024] Throughout all the Figures, same or corresponding elements
are generally indicated by same reference numerals. These depicted
embodiments are to be understood as illustrative of the invention
and not as limiting in any way. It should also be understood that
the drawings are not necessarily to scale and that the embodiments
are sometimes illustrated by graphic symbols, phantom lines,
diagrammatic representations and fragmentary views. In certain
instances, details which are not necessary for an understanding of
the present invention or which render other details difficult to
perceive may have been omitted.
[0025] Turning now to the drawing, and in particular to FIG. 1,
there is shown a longitudinal section of one embodiment of a
tensioner according to the present invention, generally designated
by reference numeral 1 and including a stationary base part 2
having an axially protruding pin 3. The pin 3 forms together with a
hub 4 of a pivot arm 5 a pivot bearing 6 which includes a sliding
bearing bush 7 arranged in an installation space bounded radially
by the hub 4 and the pin 3. Rotatably arranged via a roller bearing
9 on a free end of the pivot arm 5 is a running roller 8 which is
supported directly on a power transmitting member, e.g. a belt 10.
A force-fitting abutment of the roller 8 on the belt 10 is realized
by a torsion spring 11 having one spring end resting against the
base part 2 and another spring end resting against the pivot arm 5
for moving the pivot arm 5 to a position by which the tension force
of the belt 10 is increased. The torsion spring 11 further applies
an axial force to urge the pivot arm 5 in direction of a thrust
washer 12 which is secured in fixed rotative engagement with the
pin 3. A friction bushing 15 is disposed in an installation space
14 bounded axially by the thrust washer 12 and a support surface 13
of the pivot arm 5. The friction bushing 15 forms a damping unit
for damping an adjustment movement of the pivot arm 5 and includes
a slit 16.
[0026] As shown in FIG. 2, which is an enlarged detailed view of
the area encircled in FIG. 1 and marked "X", the friction bushing
15 is provided in the direction of the pivot arm 5 with an axially
projecting protrusion 17 which has a conical inner surface 18 and a
conical outer surface 19, whereby the conicity of the inner and
outer surfaces is the same. The protrusion 17 formfittingly engages
a circular ring shaped recess 20 of the pivot arm 5, with the inner
and outer surfaces 18, 19 resting on pertaining contact surfaces
21, 22 of the recess 20 to thereby define two conically aligned
contact zones 23, 24. When the friction bushing 15 is installed, a
gap 27 is formed between the support surface 13 of the pivot arm 5
and the friction bushing 15. A defined frictional damping between
the friction bushing 15 and the pivot arm 5 is realized by securely
fixing the friction bushing 15 on the thrust washer 12. This is
implemented by providing the friction bushing 15 with at least one
projection 25 which formfittingly engages a bore 26 of the thrust
washer 12.
[0027] FIG. 3 shows a longitudinal section of another embodiment of
a tensioner according to the present invention, generally
designated by reference numeral 31 and including a base part 32,
which includes in midsection an axial guide bush 33. Placed in the
bush 33 is a bearing pin 34 of a pivot arm 35, whereby the bush 33
defines together with the bearing pin 34 a pivot bearing 36.
Disposed in an annular gap, bounded radially by the bush 33 and the
bearing pin 34, is a sliding bearing bush 37. A roller 38 is
provided at the free end of the pivot arm 35 and is rotatably
supported by a roller bearing 39, whereby the roller 38 is
supported in force-fitting manner upon a power transmitting member,
e.g. a belt 40. The forced support of the roller 38 upon the belt
40 is realized by a torsion spring 41 having a first spring end
resting against the base part 32 and a second spring end resting
against the pivot arm 35. The axial force of the torsion spring 41
is borne by means of a thrust washer 42 which is secured in fixed
rotative engagement to the bearing pin 34. The thrust washer 42 is
hereby supported on a friction bushing 45 having a slit 46 and
placed in an installation space 44 which is bounded axially by a
support surface 43 of the base part 32 and the thrust washer
42.
[0028] As shown in FIG. 4, which is an enlarged detailed view of
the area encircled in FIG. 3 and marked "Y", the friction bushing
45 is securely fixed to the thrust washer 42 by a projection 55
which protrudes axially from an outer circumference and
formfittingly fits in a groove 56 of the thrust washer 42, thereby
establishing a desired friction damping between the friction
bushing 45 and the support surface 43 of the base part 32. The
friction bushing 45, which forms a damping unit and is also
provided with a slit 46, is provided on its side facing away from
the thrust washer 42 with an axially projecting circumferential
protrusion 47, configured to have a conical inner surface 48 and a
conical outer surface 49. The protrusion 47 is fitted in the recess
50 of the base part 32, with the recess 50 being so sized that the
protrusion 47 does not fully fill the cross sectional profile of
the recess 50 so as to establish an axial gap 57 between the
friction bushing 45 and the support surface 43 of the base part 32.
The protrusion 47 is hereby supported via the inner and outer
surfaces 48, 49 on substantially complementary conical contact
surfaces 51, 52 of the recess 50 to thereby define in concert
contact zones 53, 54.
[0029] FIG. 5 shows a sectional view of a detail showing the
tensioner of FIG. 4 with modified friction bushing 45. Parts
corresponding with those in FIG. 4 are denoted by identical
reference numerals and not explained again. The description below
will center on the differences between the embodiments. In this
embodiment, the inner and outer surfaces 48, 49 of the friction
bushing 45 converge to one another at a taper angle "a" which is
.ltoreq.35.degree., whereby the outer surface 49 is formed with a
structure in form of a longitudinal groove 58. Through the
provision of the groove 58, rubbed-off parts from the friction
bushing 45 or contact surface 52 of the recess 50 during operation
of the tensioner 31, can be expelled. As an alternative to remove
wear-based abrasions from the contact zones 53, 54, the inner and
outer surface 48, 49 may be formed with grooves in alternating
pattern.
[0030] While the invention has been illustrated and described in
connection with currently preferred embodiments shown and described
in detail, it is not intended to be limited to the details shown
since various modifications and structural changes may be made
without departing in any way from the spirit of the present
invention. The embodiments were chosen and described in order to
best explain the principles of the invention and practical
application to thereby enable a person skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
* * * * *